Silver-Catalyzed Preparation of Oxazolines from N-Propargylamides

Michael Harmata; Chaofeng Huang

doi:10.1055/s-2008-1078405

LETTER

Silver-Catalyzed Preparation of Oxazolines from N-Propargylamides

Michael Harmata*, Chaofeng Huang
Department of Chemistry, University of Missouri-Columbia, Columbia, MO 65211, USA
Fax: +1(573)8822754; e-Mail: harmatam@missouri.edu;

Abstract

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Abstract

Treatment of N-propargylamides with 5 mol% of silver hexafluoroantimonate results in the rapid formation of oxazolines in essentially quantitative yield.

Key words

N-propargylamides - silver - oxazolines - catalysis

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References and Notes

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General Procedure for the Preparation of Methylene Oxazolines from N -Propargylamides:
The amide (1 mmol) was placed in a dry flask with CH₂Cl₂ (2 mL). AgSbF₆ (5 mol%) was added in one portion with magnetic stirring. After 5-10 min, TLC showed no starting material. The reaction mixture was filtered through Celite and washed with CH₂Cl₂. The filtrate was evaporated to afford the pure (¹H NMR) product.

The starting amides were prepared by the reaction of amines with acid chlorides.

The conversion of 8 into 9 required 15 min with 2% catalyst, 1 h with 1% catalyst and 28 h with 0.1% catalyst, all reactions being conducted at r.t.

Data of selected compounds: 16: solid; mp 138-140 °C. ¹H NMR (500 MHz, CDCl₃): δ = 7.25-7.37 (m, 5 H), 5.55 (s, 1 H), 3.54 (s, 2 H), 2.31 (s, 1 H), 1.57 (s, 6 H). ¹³C NMR (125.8 MHz, CDCl₃): δ = 169.9, 134.8, 129.2, 128.9, 127.2, 87.5, 69.1, 47.6, 44.4, 28.7. IR (CH₂Cl₂): 3309, 3215, 2099, 1642, 1540, 1221, 722 cm^-1. HRMS: m/z calcd for C₁₃H₁₅NONa⁺: 224.1043; found: 224.1043. 17: solid; mp 192-193 °C. ¹H NMR (500 MHz, CDCl₃): δ = 7.26-7.34 (m, 5 H), 4.57 (d, J = 3.0 Hz, 1 H), 4.14 (d, J = 3.0 Hz, 1 H), 3.69 (s, 2 H), 1.35 (s, 6 H). ¹³C NMR (125.8 MHz, CDCl₃): δ = 167.7, 134.2, 128.8, 128.7, 127.1, 82.3, 68.5, 34.8, 29.4. IR (CH₂Cl₂): 2974, 2921, 1662, 1454, 1180, 1123 cm^-1. HRMS: m/z calcd for C₁₃H₁₅NONa⁺: 224.1043; found: 224.1044. 18: solid; mp 96-97 °C. ¹H NMR (500 MHz, CDCl₃): δ = 5.65 (s, 1 H), 2.33 (s, 1 H), 2.17 (q, J = 12.5 Hz, 2 H), 1.64 (s, 6 H), 1.14 (t, J = 12.5 Hz, 3 H). ¹³C NMR (125.8 MHz, CDCl₃): δ = 177.8, 87.3, 68.9, 47.4, 30.1, 28.9, 9.4. IR (CH₂Cl₂): 3309, 3223, 2982, 2238, 2099, 1658, 1540, 898, 718 cm^-1. HRMS: m/z calcd for C₈H₁₃NONa⁺: 162.0889; found: 162.0887. 19: solid; mp 118-120 °C. ¹H NMR (500 MHz, CDCl₃): δ = 4.81 (d, J = 3.5 Hz, 1 H), 4.38 (d, J = 3.5 Hz, 1 H), 2.50 (q, J = 3.0 Hz, 2 H), 1.45 (s, 6 H), 1.32 (t, J = 3.0 Hz, 3 H). ¹³C NMR (125.8 MHz, CDCl₃): δ = 171.6, 164.6, 86.0, 68.0, 30.1, 22.9, 9.7. IR (CH₂Cl₂): 3624, 3411, 2986, 1654, 1180, 665 cm^-1. HRMS: m/z calcd for C₈H₁₃NOH⁺: 140.1070; found: 140.1068. 20: solid; mp 96-98 °C. ¹H NMR (500 MHz, CDCl₃): δ = 6.84 (dt, J = 9.0, 14.5 Hz, 1 H), 5.92 (s, 1 H), 5.81 (d, J = 14.5 Hz, 1 H), 2.34 (s, 1 H), 1.83 (d, J = 9.0 Hz, 3 H), 1.67 (s, 6 H). ¹³C NMR (125.8 MHz, CDCl₃): δ = 165.0, 139.9, 125.3, 87.2, 68.9, 47.3, 28.9, 17.5. IR (CH₂Cl₂): 3293, 3239, 2974, 2108, 1634, 1540, 1233, 967 cm^-1. HRMS: m/z calcd for C₉H₁₃NONa⁺: 174.0890; found: 174.0889. 21: oil. ¹H NMR (500 MHz, CDCl₃): δ = 6.84 (dt, J = 6.0, 15.5 Hz, 1 H), 6.07 (d, J = 15.5 Hz, 1 H), 4.72 (d, J = 3.0 Hz, 1 H), 4.27 (d, J = 3.0 Hz, 1 H), 1.94 (d, J = 6.0 Hz, 3 H), 1.41 (s, 6 H). ¹³C NMR (125.8 MHz, CDCl₃): δ = 165.9, 161.3, 143.3, 117.6, 83.5, 68.1, 29.8, 18.5. IR (CH₂Cl₂): 2970, 1674, 1307, 1184, 972, 661 cm^-1. HRMS: m/z calcd for C₉H₁₃NONa⁺: 174.0889; found: 174.0886. 22: solid; mp 48-49 °C. ¹H NMR (500 MHz, CDCl₃): δ = 5.81 (s, 1 H), 3.61 (t, J = 6.0 Hz, 2 H), 2.34 (t, J = 6.0 Hz, 2 H), 2.11 (tt, J = 6.0, 6.0 Hz, 2 H), 1.64 (s, 6 H). ¹³C NMR (125.8 MHz, CDCl₃): δ = 170.8, 86.9, 67.1, 47.5, 44.4, 33.5, 28.9, 27.9. IR (CH₂Cl₂): 3350, 3239, 2994, 2108, 1646, 1540, 1221 cm^-1. HRMS: m/z calcd for C₉H₁₄ClNONa⁺: 210.0656; found: 210.0651. 23: oil. ¹H NMR (500 MHz, CDCl₃): δ = 4.60 (d, J = 3.0 Hz, 1 H), 4.10 (d, J = 3.0 Hz, 1 H), 3.63 (t, J = 6.0 Hz, 2 H), 2.56 (t, J = 7.0 Hz, 2 H), 2.17 (tt, J = 6.0, 7.0 Hz, 2 H), 1.35 (s, 6 H). ¹³C NMR (125.8 MHz, CDCl₃): δ = 167.5, 162.9, 82.2, 68.3, 43.8, 29.5, 28.2, 25.2. IR (CH₂Cl₂): 2974, 2929, 1679, 1192, 1127, 963 cm^-1. HRMS: m/z calcd for C₉H₁₄ClNOH⁺: 188.0837; found: 188.1277. 24: solid; mp 106-107 °C. ¹H NMR (500 MHz, CDCl₃): δ = 5.67 (s, 1 H), 2.32 (s, 1 H), 1.66 (s, 6 H), 1.20 (s, 9 H). ¹³C NMR (125.8 MHz, CDCl₃): δ = 177.4, 87.4, 68.8, 47.4, 38.9, 28.7, 27.4. IR (CH₂Cl₂): 3362, 3288, 2998, 1650, 1523, 1356, 1209 cm^-1. HRMS: m/z calcd for C₁₀H₁₇NONa⁺: 190.1202; found: 190.1200. 25: oil. ¹H NMR (500 MHz, CDCl₃): δ = 4.56 (d, J = 2.5 Hz, 1 H), 4.10 (d, J = 2.5 Hz,
1 H), 1.33 (s, 6 H), 1.27 (s, 9 H). ¹³C NMR (125.8 MHz, CDCl₃): δ = 169.6, 168.5, 80.9, 68.2, 32.9, 29.5, 27.4. IR (CH₂Cl₂): 3419, 2974, 1646, 1180, 1094 cm^-1. HRMS: m/z calcd for C₁₀H₁₇NONa⁺: 190.1202; found: 190.1042. 26: solid; mp 108-110 °C. ¹H NMR (500 MHz, CDCl₃): δ = 8.23 (d, J = 9.0 Hz, 2 H), 7.93 (d, J = 9.0 Hz, 2 H), 5.57 (s, 1 H), 2.43 (s, 1 H), 1.78 (s, 6 H). ¹³C NMR (125.8 MHz, CDCl₃): δ = 164.5, 149.4, 140.3, 128.1, 123.6, 86.4, 69.8, 49.3, 28.8. IR (CH₂Cl₂): 3289, 2982, 1654, 1527, 1352, 845 cm^-1. HRMS: m/z calcd for C₁₂H₁₂N₂O₃Na⁺: 255.0740; found: 255.0738. 27: oil. ¹H NMR (500 MHz, CDCl₃): δ = 8.30 (d, J = 8.0 Hz, 2 H), 8.18 (d, J = 8.0 Hz, 2 H), 4.80 (d, J = 3.0 Hz, 1 H), 4.33 (d, J = 3.0 Hz, 1 H), 1.48 (s, 6 H). ¹³C NMR (125.8 MHz, CDCl₃): δ = 167.2, 158.2, 149.6, 132.6, 129.1, 123.6, 83.5, 69.6, 29.5. IR (CH₂Cl₂): 3427, 3105, 2982, 1646, 1597, 1519, 1307, 1066 cm^-1. HRMS: m/z calcd for C₁₂H₁₂N₂O₃Na⁺: 255.0740; found: 255.0739.